The present invention relates in general to a towed tank for holding a liquid, and in particular to a towed fuel tank that is submergible, collapsible, and steerable.
Generally, all fuel burned by a ship is carried on board. The amount of fuel carried on board depends upon the design range of the ship. A typical surface combatant will be about 20% fuel by weight. The fuel load has a great impact on the design of the ship in regard to space, weight, and the ultimate size and cost of the ship. The ship design is often limited by the fuel load, which must be carried on board.
Fuel is stored low in a ship due to stability requirements. As the fuel is used, it generally is replaced by seawater, to maintain the ship's static stability. Often, depending on the design range, significant amounts of fuel must occupy otherwise useable space, thus increasing the size and cost of the ship.
Naval ships are designed for an expected life period of 30 years and longer. The design of naval ships is performed 5-10 years prior to their use and is based on projected mission requirements. A major element of ship design is range. The design range of a ship limits the utility of that ship to missions whose range is less than or equal to the design range. As a ship ages, its fuel efficiency generally decreases because of the decreasing efficiencies of the fuel users, such as boilers, internal combustion engines, etc. Thus, as a ship ages, it becomes less likely that it can meet the range requirements of a modern mission.
Furthermore, naval ships are refueled at sea by oilers. If a particular mission requires stealth, then the mission may be jeopardized by the need for a refueling ship to enter the stealth zone.